Floating-piston internal-combustion machine



K. H. w. HELLWEG 3,183,900

FLOATING-PISTON INTERNAL-COMBUSTION MACHINE Filed Aug. 2. 1961 May 18, 1965 2 Sheets-Sheet 1 y 3, 1965 K. H. w. HELLWEG 3,183,900

FLOATING-PISTON INTERNAL-COMBUSTION MACHINE Filed Aug. 2 1961 2 Sheets-Sheet 2 United States Patent 3,183,909 FLOATING-PISTON IN TERNAL-COMBUSTION MACHINE 35,386 9 Claims. (Cl. 123-41.78)

This invention relates to internal-combustion motors and generators of the type having two opposed floating motor pistons reciprocable in a common cylinder housing formed with spaced air intake and gas exhaust ports adapted to intercommunicate through the cylinder space between the pistons when both pistons are about to reach the outermost end of their common outward stroke. Injector means are provided for injecting a suitable fuel into the cylinder space between the floating motor pistons for combustion as the pistons are attaining the end of the inward stroke of their cycle to provide the energy propelling them on their outward stroke. Each motor piston is connected by a rod to a related compressor piston reciprocable in a compressor cylinder positioned beyond a related end of the common motor cylinder so that the compressor pistons participate bodily in the reciprocation of the respective motor pistons. Air (or other gas) is drawn into the compressor cylinders on the inward stroke of the pistons while on the outward stroke this air or gas is compressed by the compressor pistons and discharged under pressure into the motor cylinder through the aforesaid intake ports to serve as the combustion-sustaining and scavenging medium. A body of air or gas is also present in the motor cylinder between the rear face of each motor piston and the related end wall of the cylinder to provide a resilient cushioning means storing energy at the outgoing stroke of the motor pistons and restoring said energy to propel the pistons on their ingoing stroke. The combustion exhaust gases which are discharged out of the motor cylinder through the aforesaid exhaust ports, which gases are at high temperature and pressure (cg. kg./cm. gauge) may be fed to a suitable receiver apparatus, e.g. a gas turbine.

Machines of this kind are very advantageous due to their high efficiency ratio and excellent mechanical as well as thermodynamic performance, but their construction poses a number of problems which have not heretofore been solved in an entirely satisfactory manner. One of these problems relates to the high differential thermal expansion effects which occur in the casing structure of V such a machine due to the considerable temperature differences between the different parts thereof, especially since it is advantageous to provide water jacket or equivalent cooling means around at least the central part of the motor cylinder where fuel combustion occurs. It is one object of this invention to provide an improved construction of such a machine in which such differential expansion will be properly taken care of in a simple and effective way.

In machines of the kind specified, the air compressed by the compressor pistons is usually stored in a suitable space defined in the casing and from which said air is discharged through the intake ports into the motor cylinder. In prior machines, this stored air has frequently been tainted with lubricating oil'from the compressor units and other parts of the machine, with objectionable results. An object of the invention is to prevent con- A further object is to provide an improved disposition of the casing structure of such a machine whereby all or most of the components to which access should be had at relatively frequent intervals for maintenance and servicing are positioned in compartments of the casing open to atmospheric pressure and hence providable with large and convenient access apertures, thereby greatly facilitating such operations; the components involved may preferably include the following: fuel injector, motor piston lubricators, cooling water inlet and outlet.

A further object is to provide improved sliding seal means between relatively displaceable parts of the machine whereby identification and replacement of a defective seal will be facilitated.

While further specific objects will appear, a general object of this invention can be stated as lying in the provision of an improved construction of a floating-piston internal-combustion machine, the improvements chiefly concerning the casing structure of the machine, whereby the operating efficiency will be increased, and construction and maintenance facilitated.

In accordance with an aspect of the invention, there is provided in a machine of the kind specified an annular casing assembly surrounding the motor cylinder housing and defining a plurality of separate annular compartments spaced axially of said housing, which compartments include a central compartment and a pair of end compartments all open to atmosphere, a first further compartment between one side of the central compartment and one end compartment and surrounding the said intake ports, and a second further compartment between the other side of the central compartment and the other end compartment and surrounding said exhaust ports; the fuel injection means being positioned in said central compartment and extending into the motor cylinder housing; means connecting said first further compartment with the outer ends of both compressor cylinder housings so serve as an air storage capacity for supplying compressed air through the intake ports to the motor cylinder; and means attached to said second further compartment for discharging exhaust gases issuing from said exhaust ports.

Preferably, the second further compartment is also connected to said outer ends of the compressor cylinder housings and the exhaust gas discharging means comprises a conduit extending through but sealed from said second further compartment and connecting with said exhaust ports; this arrangement has an additional advantage in that the exhaust gas discharge conduit is exposed to a lesser pressure difference across its Walls than were its outer wall surface exposed to atmospheric pressure.

According to a feature of the invention, the casing assembly is arranged around said motor cylinder housing for axial sliding displacements relatively thereto under differential thermal expansion effects and is secured to the motor cylinder housing at substantially only a single axial position to permit such expansion effects.

In a preferred construction the casing assembly is in three parts, including a central part and two end parts secured to opposite ends of the central part and to inner ends of the related compressor cylinder housings, and said central part includes a pair of axially spaced transverse walls subdividing it into said central and said further compartments, while said end parts define said end compartments.

An exemplary embodiment will now be described for purposes of illustration only, with reference to the accompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view of the machine, and

FIG. 2 is a cross section on line IIII of FIG. 1.

V The floating-piston machine illustrated in the drawings 3 comprises a motor cylinder housing 4- in which a pair of similar opposed floating pistons 1 and 1 are slidably mounted, with piston rods 2 and 2' projecting in opposite directions therefrom. The motor cylinder housing 4 is surrounded by an assembly of three annular casing parts assembled around the housing 4 so as to provide a stack in the axial direction of said cylinder housing. The three stacked annular casing parts include a so-called motor casing part 22 surrounding the central portion of the cylinder housing 4, and two end casing parts 23 and 23' surrounding respective end portions of housing 4.

The central or motor casing part 22 comprises a pair of axially spaced, parallel, transverse walls 31 and 34 which divide it into three compartments; the central compartment 49 and two side compartments l4 and 32. To permit relative thermal expansion in view of the differential temperatures set up in the system in operation, the annular casing parts 22, 23 and 23 are only connected with the cylinder housing 4 at one point axially of the length of the assembly. In the specific embodiment, only the motor casing part 22 is rigidly connected with the motor cylinder housing 4- at a single point of its length, specifically by being bolted or pinned as at 72 to an annular flange 71 extending radially outwardly from the housing 4. The end casing sections 23 and 23' are each secured to the respective ends of the motor casing 22 by bolts as at '74 and 75 extending through holes formed in mating flanges of the respective casing sections. The casing sections 23, 23' define the so-called end compartments 3Q, 41, respectively, of the annular casing assembly. Similarly secured through mating flanges beyond the axially outermost ends of the end casing sections 23 and 23' are the compressor cylinder housings 11 and 11' in which the large-diameter compressor pistons 3 and 3' respectively are slidable. The compressor pistons 3 and 3' are centrally secured to the free ends of the piston rods 2 and 2. The motor cylinder housing 4 is separated at each end from the respective compressor cylinder housings 11 and 11 by cylinder heads or end plates 7 and 7' secured through any suitable means to the outer faces 17 and 17' of the end casing sections 23 and 23, and spaced by small axial clearance spaces as shown from the related outer ends of the cylinder housing 4 to allow for differential thermal expansion. The piston rods 2 and 2 slidably extend through packing glands 8 and 8' formed in central openings of the cylinder heads 7 and 7'.

Formed in the peripheral wall of motor cylinder housing 4 intermediate between the midpoint of the cylinder housing and the left-hand end of it, are a set of air intake ports (only one shown), for the intake of combustion and scavenging air (or gas) into the motor cylinder as will later appear. Formed in said cylinder housing wall intermediate the midpoint and the other, right-hand, end of it are a set of exhaust gas discharge ports 6 (only one shown). The air intake ports 5 open at their outer ends into the compartment 14 defined between the motor casing section wall 31 and wall 30 of the end casing section 23, which compartment communicates through a longitudinal conduit 1515 positioned radially beyond the casing assembly, with the outer ends of both compressor cylinder spaces as will be further described. The exhaust ports 5 open at their outer ends into a radially extending discharge conduit 33. It will be understood that in operation each of the spaces 16 and iii defined between the outer end faces 9, 9' of the motor pistons 1 and 1', and the related cylinder heads 7 and 7', is filled with a body of gas which acts as an elastic cushion, energy being stored in said bodies of gas on the outward stroke inward stroke of the piston assemblies. At the outward stroke of the pistons, said air is compressed and discharged through the outwardly opening check valves 13 and 13' into the afore-mentioned conduits 15, 15' and thence into the space 14 and through air intake ports 5 into the motor space between pistons 1 and 1' to serve as combustion and scavenging air. Space 14 thus serves as an air storage capacity. The spaces 18, 18' defined between the rear faces 16, 16' of the compressor pistons 3 and 3, and the outer walls 17, 17 of the end casing sections 23, 23' are connected by way of outwardly opening check valves 19, 19' with the end compartments 39, 41 and thence to the atmosphere by way of wide apertures such as 50 and 52 formed in the end casing sections 23, 23.

For positively synchronizing the reciprocations of both piston assemblies there are provided rackbars 2t) and 20 extending from the rear faces of the compressor pistons '3 and 3 and formed with rack teeth which mesh with a common gear 21 journalled in a compartment 53 of the central casing section 22.

For cooling the motor cylinder housing 4 means are provided defining annular water passages 24, 24' surrounding the respective ends of said housing and a central annular water jacket chamber or recess 25 surrounding an intermediate length of the housing and connected with said end passages 24, 24' through the axial passages 27 and 28. Cooling water from a suitable source is delivered into the end passages 24 and 24' by the pipes 26, 26 and is discharged from recess 25 through the water discharge pipe 29.

Generally symmetrically to the air storage capacity 14 another capacity is provided by the compartment 32 between the radial walls 34 and 35 of the casing assembly. The aforementioned exhaust gas discharge pipe 33 extends outwardly through the compartment 32. Compartment 32 is connected with the compressed air flow line 15 by a conduit 36 in which is interposed a check valve 37 opening into the space 32, so that the pressure in space 32 is the maximum pressure of the compressed air from the compressor cylinders 11 and 11. The exhaust gas discharge line 33 is secured to in an opening formed through the wall at the motor casing section 22 and at its inner end connects with an annular exhaust manifold secured around the motor cylinder housing 4 over the exhaust ports 6, by means of removable sealing rings 38. It will be seen that the walls of the exhaust manifold or discharge line 33 are exposed on their inner one side, to the pressure of the exhaust gases and are exposed on their outer side to the compressed-air pressure prevailing in space 32. The pressure differential across the exhaust line walls is thereby substantially lower than were said line surrounded by atmospheric pressure as in most prior constructions. Thus the said exhaust line or manifold 33 can be made of lighter material, and construction is facilitated and cheapened.

The end compartment 39 defined between the casing walls 17 and 30, the other end compartment 41 between walls 35 and 17', and the central compartment 40 between walls 31 and 34 all communicate with atmosphere through the large-sized respective apertures 50, 52 and 51. The separate space 53 surrounding the racks and gear is isolated from atmosphere through suitable sealing means, and may contain a relative vacuum.

In the central compartment 40 of the middle casing section 22 is mounted a fuel injector nozzle 42 which is arranged to discharge into the central region of motor cylinder housing 4. A lubricator nozzle 43 is also mounted in said compartment for lubricating the sliding surfaces of the cylinder 4 and pistons 1 and 1'. As previously mentioned the cooling water discharge pipe 29 also extends through said space 40. Because the space 40 is at atmospheric pressureand is readily accessible through the wide aperture 51, it will be seen that the mounting, maintenance and removal or replacement of the components just listed, especially fuel injector and lubricator, are greatly facilitated. It will be noted that in this example a further lubricator 78 is shown mounted in the end space 19 which also being at atmospheric pressure facilitates servicing of thislubricator.

The requisite seal between the motor cylinder housing 4 and the'surrounding casingsections 22,23 and 23 is provided by annular rubber seals or the like, e.g. O-rings as shown at 55, 56, 57, 58, 61 and 62, which enable slight axial shifting between the mating surfaces for taking up differential thermal expansion. Similarly a tight seal is maintained between the water jacket spaces 24 and 24' and the air-cushioning cylinder spaces and 10 by means of the seal rings 63, 64, 63' and 64'. As shown, between the axially spaced seal rings 63 and 64, and between their counterparts 63' and 64' there is an annular groove 44 and 44, which grooves are connected through ports 45 and 45 with the respective compartments 39 and 41 and thence with atmosphere. Should the seals 63 or 63' be defective due to wear or other causes, air will leak out thnough the ports 45 or 45 from the space 10 or 10' past the defective seal 63 or 63' and through ports 45 or 45' into the atmospheric compartment 39 or 41; on the other hand, should the seal 64 or 64' be defective, water will leak out through the same ports 45 or 45 from the water jacket channels 24 or 24'. Thus a defective seal can immediately be identified.

In similar fashion, between the axially spaced seal rings 55 and 56 sealing the mating surfaces of cylinder housing 4 and easing section 22, is anannular groove 66 communicating through a conduit 67 with the space 40. Water leaking out through the passage 67 will indicate a defect in seal ring 56, while air leaking out through said passage will indicate a defective seal 55.

Furthermore, each of the sealing gasket means 8 and 8 through which the piston rods slide in the cylinder heads 7 and 7' comprises two sets of seal rings 8a and 8b on one side, and 8a and 812' on the other, each separated from the other by an annular groove 68 or 68' communicating through a passage 69 or 69' with the atmospheric space 39 or 41. If air is found to leak out of a passage 69 or 69 this will indicate a leak in the related seal ring 8b or 8b respectively, whereas if air is found to leak in through either of said passages this will provide an indication that the seal ring 8a or 8a respectively, is defective (owing to the action of check valves 19, 19').

On a similar principle again, there are provided the spaced seal rings 57 and 58 on one side, and 61 and 62 on the other, between the cylinder housing 4 and each of the end casing sections 23 and 23', with an annular groove 83 and 84 therebetween, which groove communicates through the ports 81 or 82 with the atmospheric compartment 39 or 41 respectively. Water leaking out through a port 81 or 82 will indicate a leak in the related seal 57 or 62, while air or gas leaking out through the same ports will indicate a defect in seal 58 or 61.

The provisions of the invention just described are extremely advantageous in that they provide a means not only of quickly detecting the presence of a leak but also immediately identifying the leaky seal. Instead of having to dismantle many parts of the machine and examining the seals one by one until the faulty seal is located, only the section of the machine containing the seal identified as being at fault need be removed for replacement of the faulty seal. Maintenance is thus greatly facilitated.

It will be noted that the space 53 containing the synchronizing racks and the gear 21 meshing with them will normally be filled with oil vapour due to the lubrication of the gearing. It is important to prevent such oil vapour from entering the spaces 18 and 18' in the compressor cylinders behind the compressor pistons, since otherwise such oil could readily be carried over into the active compressor spaces in front of pistons 3 and 3 and thence into the air storage capaicty 14 with a consequent soiling of the delicate check-valves 13 and 13 and other objectionable results. To avoid this the packing gland assemblies 46 and 47, and 46 and 47' are provided around the rack bars. Between the two packings such as 46 and 47 on a common rack bar, the rack bar is readily visible through the openings such as 39, so that any abnormal presence of oil thereon is readily detected and can be corrected by replacement of the corresponding packing 46 or 46', before damage has been done.

It will be understood that various changes may be made inthe exemplary embodiment illustrated and described. Thus various of the features disclosed may have utility separately from other of the features.

What is claimed is:

l. A floating-piston type combustion machine comprising, a cylindrical motor cylinder housing, a closure at each each thereof, a separable compressor cylinder housing at each end of the motor cylinder housing, a pair of opposed pistons within the motor cylinder housing, a pistonrod extending from each piston through the related end closure and connected to the related compressor piston, a plurality of annular compartments spaced axially of the motor cylinder housing and supported thereon, said compartments being positioned with one adjacent each compressor cylinder housing and one central therebetween to define a first and second further compartment, an air inlet passage in the motor cylinder from the first further compartment, an exhaust passage from the motor cylinder to the second further compartment, means connecting said first further compartment to at least one of the compressor cylinders to feed air to said first further compartment, the compartments adjacent to each of the compressor cylinder housing and the central compartment being opened to the atmosphere, conduit means leading from the exhaust passage through said second further compartment and closing said second further compartment to atmosphere, and means connecting said second further compartment to one of the compressor cylinders to feed air thereto.

2. The invention defined in claim 1 wherein said air feeding means interconnects each of said first and second further compartments.

3. The invention defined in claim 2 including check valve means in said air feeding means, said check valve opening to permit air feeding only.

4. In a floating-piston type combusion machine including a motor cylinder housing and a pair of opposed motor pistons reciprocable therein; a pair of compressor cylinder housings, secured to and sealed from the opposite ends of said motor cylinder housing and a pair of compressor pistons reciprocable therein; piston rods connecting each motor piston, with a related compressor piston; fuel combustion means centrally of said motor cylinder; and air intake and gas exhaust ports formed in a side wall of the motor cylinder housing at spaced positions such that said ports intercommunicate at an outermost point in each motor piston reciprocatory cycle; the improvement comprising an annular casing assembly surrounding said motor cylinder housing and defining a plurality of separate annular compartments spaced axially of the housing and including a central compartment and a pair of end compartments all open to atmosphere, a first further compartment between one side of the central compartment and one end compartment and surrounding said intake ports, and a second further compartment between the other side of the central compartment and the other end compartment and surrounding said exhaust ports; means connecting said first further compartment with the outer end of at least one of said pair of compressor cylinder housings to supply compressed air through said intake ports on outward reciprocation of said compressor pistons; and means in said second further compartment for discharging exhaust gases issuing from said exhaust ports, conduit means connecting said second further compartment to said outer end of at least one compressor cylinder housing, and check valve means in the conduit means to permit airflow only from said first to said second further compartment, and a gas discharge conduit connecting with said exhaust ports in the motor cylinder housing and extending through said second further compartment and sealed therefrom.

5. A free piston type combustion machine comprising a motor cylinder having intake ports and exhaust ports, a pair of opposed motor pistons reciprocable in said motor cylinder, an annular casing assembly surrounding the latter, a pair of compressor cylinders secured to both ends of said annular casing assembly, a pair of opposed compressor pistons connected to said motor pistons and reciprocable in said compressor cylinders, said annular casing assembly being portioned in a plurality of axially spaced annular compartments, one of them surrounding said intake ports, a second of them surrounding said exhaust ports, the two latter compartments being separated and surrounded by other compartments opened to the atmosphere, said annular casing being rigidly connected to said motor cylinder in a single radial plane with respect to the axis of the latter, slidable and sealed contacts being provided between said motor cylinder and respectively the compressor cylinders and the other internal parts of said annular casing assembly.

6. A free piston type combustion machine according to claim 5 wherein said internal parts are essentially constituted by the internal faces of those of said compartments which are opened to the atmosphere.

7. A free piston type combustion machine according to claim 5 wherein the outer face of said motor cylinder and the inner face of said internal parts, are so shaped as to form sealed annular cooling fluid chambers, means being provided in said annular casing assembly to deliver a cooling fluid into said annular chambers and to discharge it therefrom.

8. A free piston type combustion machine according to claim 5 wherein means are provided in the compartments of the annular casing assembly opened to the atmosphere to check the seal of all of said slidable contacts between said motor cylinder and said annular casing assembly.

9. A freepiston type combustion machine according to claim 5 including piston rods connecting said motor piston to the related compressor piston, cylinderheads at both ends of said motor cylinder and secured to said annular casing assembly, openings in said cylinder heads in which said piston rods are sliding, clearances between the ends of said motor cylinder and said cylinder heads to allow relative sliding of said motor cylinder with respect to said annular casing assembly under difierential thermical expansion.

References Cited by the Examiner UNITED STATES PATENTS 1,862,255 6/32 Coleman 184-65 2,000,265 5/35 Vickers 27717 2,406,037 8/40 Ramsey 123-46 2,558,444 6/51 Kunz 123--46 2,581,600 1/52 Pescara 12346 2,952,251 9/60 Braun 12346 3,031,972 5/62 Janicke 23056 FRED E. ENGELTHALER, Primary Examiner.

KARL J. ALBRECHT, SAMUEL LEVINE, Examiners. 

5. A FREE PISTON TYPE COMBUSTION MACHINE COMPRISING A MOTOR CYLINDER HAVING INTAKE PORTS AND EXHAUST PORTS, A PAIR OF OPPOSED MOTOR PISTONS RECIPROCABLE IN SAID MOTOR CYLINDER, AN ANNULAR CASING ASSEMBLY SURROUNDING THE LATTER, A PAIR OF COMPRESSOR CYLINDERS SECURED TO BOTH ENDS OF SAID ANNULAR CASING ASSEMBLY, A PAIR OF OPPOSED COMPRESSOR PISTONS CONNECTED TO SAID MOTOR PISTONS AND RECIPROCABLE IN SAID COMPRESSOR CYLINDERS, SAID ANNULAR CASING ASSEMBLY BEING PORTIONED IN A PLURALITY OF AXIALLY SPACED ANNULAR COMPARTMENTS, ONE OF THEM SURROUNDING SAID INTAKE PORTS, A SECOND OF THEM SURROUNDING SAID EXHAUST PORTS, THE TWO LATTER COMPARTMENTS BEING SEPARATED AND SURROUNDED BY OTHER COMPARTMENTS OPENED TO THE ATMOSPHERE, SAID ANNULAR CASING BEING RIGIDLY CONNECTED TO SAID MOTOR CYLINDER IN A SINGLE RADIAL PLANE WITH RESPECT TO THE AXIS OF THE LATTER, SLIDABLE AND SEALED CONTACTS BEING PROVIDED BETWEEN SAID MOTOR CYLINDER AND RESPECTIVELY THE COMPRESSOR CYLINDERS AND THE OTHER INTERNAL PART OF SAID ANNULAR CASING ASSEMBLY.
 7. A FREE PISTON TYPE COMBUSTION MACHINE ACCORDING TO CLAIM 5 WHEREIN THE OUTER FACE OF SAID MOTOR CYLINDER AND THE INNER FACE OF SAID INTERNAL PARTS ARE SO SHAPED AS TO FORM SEALED ANNULAR COOLING FLUID CHAMBERS, MEANS BEING PROVIDED IN SAID ANNULAR CASING ASSEMBLY TO DELIVER A COOLING FLUID INTO SAID ANNULAR CHAMBERS AND TO DISCHARGE IT THEREFROM. 